Semiconductor devices are commonly found in modern electronic products. Semiconductor devices vary in the number and density of electrical components. Discrete semiconductor devices generally contain one type of electrical component, for example, light emitting diode (LED), small signal transistor, resistor, capacitor, inductor, and power metal oxide semiconductor field effect transistor (MOSFET). Integrated semiconductor devices typically contain hundreds to millions of electrical components. Examples of integrated semiconductor devices include microcontrollers, microprocessors, charged-coupled devices (CCDs), solar cells, and digital micro-mirror devices (DMDs).
Semiconductor devices perform a wide range of functions such as signal processing, high-speed calculations, transmitting and receiving electromagnetic signals, controlling electronic devices, transforming sunlight to electricity, and creating visual projections for television displays. Semiconductor devices are found in the fields of entertainment, communications, power conversion, networks, computers, and consumer products. Semiconductor devices are also found in military applications, aviation, automotive, industrial controllers, and office equipment.
Semiconductor devices exploit the electrical properties of semiconductor materials. The atomic structure of semiconductor material allows its electrical conductivity to be manipulated by the application of an electric field or base current or through the process of doping. Doping introduces impurities into the semiconductor material to manipulate and control the conductivity of the semiconductor device.
A semiconductor device contains active and passive electrical structures. Active structures, including bipolar and field effect transistors, control the flow of electrical current. By varying levels of doping and application of an electric field or base current, the transistor either promotes or restricts the flow of electrical current. Passive structures, including resistors, capacitors, and inductors, create a relationship between voltage and current necessary to perform a variety of electrical functions. The passive and active structures are electrically connected to form circuits, which enable the semiconductor device to perform high-speed calculations and other useful functions.
Semiconductor devices are generally manufactured using two complex manufacturing processes, that is, front-end manufacturing, and back-end manufacturing, each involving potentially hundreds of steps. Front-end manufacturing involves the formation of a plurality of semiconductor die on the surface of a semiconductor wafer. Each semiconductor die is typically identical and contains circuits formed by electrically connecting active and passive components. Back-end manufacturing involves singulating individual semiconductor die from the finished wafer and packaging the die to provide structural support and environmental isolation. The term “semiconductor die” as used herein refers to both the singular and plural form of the words, and accordingly can refer to both a single semiconductor device and multiple semiconductor devices.
One goal of semiconductor manufacturing is to produce smaller semiconductor devices. Smaller devices typically consume less power, have higher performance, and can be produced more efficiently. In addition, smaller semiconductor devices have a smaller footprint, which is desirable for smaller end products. A smaller semiconductor die size can be achieved by improvements in the front-end process resulting in semiconductor die with smaller, higher density, active and passive components. Back-end processes may result in semiconductor device packages with a smaller footprint by improvements in electrical interconnection and packaging materials.
One approach to back-end processing that more efficiently produces packaged semiconductor devices is the use of panelized packaging, in which a number of semiconductor die are formed into a panel and processed simultaneously at a level of a reconstituted wafer or panel. Panelized packaging can be used in back-end manufacturing for forming embedded die packages. One form of panelized packaging used to package semiconductor die is FOWLP. FOWLP involves placing multiple semiconductor die “face down” or with an active surface of the semiconductor die oriented toward a temporary carrier or substrate, such as a temporary tape carrier. The semiconductor die and substrate or carrier is overmolded with an encapsulant, such as an epoxy molding compound, using, for example, a compression molding process. After molding, the carrier tape is removed to expose the active surface of the multiple semiconductor die formed together as a reconstituted wafer. Subsequently, a wafer level chip scale package (WLCSP) build-up interconnect structure, typically including a redistribution layer (RDL), is formed on top of the reconstituted wafer or panel. Conductive bumps are then formed over the build-up interconnect structure as a ball grid array (BGA), which is attached to the reconstituted wafer. After formation of the BGA, the reconstituted wafer is singulated to form individual semiconductor devices or packages. Sometimes, semiconductor die are displaced in the process of being mounted to the substrate and are also displaced during the overmolding processes. Displacement of the semiconductor die, including rotation of the semiconductor die, can result in defective semiconductor packages that decrease package quality and reliability and further increase package yield loss.
Another area of back-end manufacturing that allows for the formation of embedded die packages is the embedding of semiconductor die in substrates, such as printed circuit board (PCB) type structure or printed wiring board panel, wherein the semiconductor die is embedded in inner layers of a multi-layer substrate. Embedded semiconductor die packages can be formed by introducing thinned semiconductor die and buried semiconductor die into inner layers of substrates. Semiconductor die can be buried in cavities within the substrate inner layers, and can also be added to a surface of an inner layer of a substrate, after which build-up technology can then be used to construct a board sandwich with layers disposed above and below the semiconductor die. Including semiconductor die within substrates can supports an industry need of reducing footprints and improving signal performance while advancing the concept of three-dimensional (3D) packaging as part of package integration.